Liquid flows in cyclonic particle separation chambers

ABSTRACT

In an example, a filtration apparatus includes a cyclonic particle separation chamber having an inner surface and a liquid source. The liquid source may be to supply liquid to provide a flow of liquid on the inner surface.

BACKGROUND

Cyclonic particle separation apparatus may be used to separate particlesfrom an air flow. For example, industrial and domestic vacuum cleanersand filters may make use of cyclonic particle separation apparatus.

In examples of such apparatus, air may be drawn into a cylindrical orconical chamber and caused to flow in a spiral. Particles suspended inthe air, being heavier, move towards the edge of the chamber. Theparticles then tend to strike the chamber walls, fall and collect at thebottom of the chamber.

BRIEF DESCRIPTION OF DRAWINGS

Non-limiting examples will now be described with reference to theaccompanying drawings, in which:

FIGS. 1 and 2 are examples of filtration apparatus;

FIG. 3 is an example method for filtering an air flow;

FIG. 4 is an example method for recirculating a liquid; and

FIG. 5 is an example of an additive manufacturing apparatus.

DETAILED DESCRIPTION

Cyclonic particle separation apparatus are used in vacuum cleaning ofsurfaces such as floors, textiles and the like and in ‘air scrubbing’ inwhich dust or other particles may be removed from the air.

In some examples herein, a cyclonic ‘vacuum’ apparatus is used to removeparticles suspended in the air removed from a chamber of an additivemanufacturing apparatus, which may for example comprise a fabricationchamber, or another chamber of an apparatus for use in additivemanufacturing processes, such as a chamber in which objects arepost-processed to remove unfused material, or a build materialprocessing (e.g. mixing) chamber, or the like. Additive manufacturingtechniques may generate a three-dimensional object on a layer-by-layerbasis through the solidification of a build material which may be apowder-like granular material, which may for example be a plastic,ceramic or metal powder. In examples of such techniques, build materialis supplied in a layer-wise manner and a solidification method mayinclude heating the layers of build material to cause melting inselected regions.

In some examples, selective solidification is achieved throughdirectional application of energy, for example using a laser or electronbeam. In other examples, at least one print agent may be selectivelyapplied to the build material, and may be liquid when applied. Forexample, a fusing agent having a composition which absorbs energy (alsotermed a ‘coalescence agent’ or ‘coalescing agent’) may be selectivelydistributed onto portions of a layer of build material in a patternderived from data representing a slice of a three-dimensional object tobe generated (which may far example be generated from structural designdata). When energy (for example, heat) is applied to the layer, thebuild material coalesces and solidifies to form a slice of thethree-dimensional object in accordance with the pattern. In othertechniques, other solidification methods, such as chemicalsolidification methods or binding materials, may be used.

Where powder-like materials are used in object manufacture, some of thepowder may become dispersed, for example within the air inside thefabrication chamber, or some other chamber used in additivemanufacturing. In some such examples, a vacuum system may be used toextract air from the chamber (for example, to provide cooling within thefabrication chamber, in particular when methods of manufacture which useheating in object generation are used), and the vacuum system maycomprise a particle separation apparatus. This particle separationapparatus may be used to remove particles of build material which couldotherwise be expelled outside the machine, creating a particle filledatmosphere which may for example be inhaled by machine operators. Insome examples, such apparatus may comprise micro filters, cartridgefilters, or the like. In examples set out herein, cyclonic particleseparation apparatus may be used to separate build material from theextracted air.

Such cyclonic particle separation apparatus may also be used to separatesmall particles from an air flow in a variety of circumstances. Cyclonicparticle separation apparatus is resistant to clogging but mayeffectively filter a relatively small range of particle sizes from anair flow. To overcome this, it has been proposed to provide multiplecyclonic chambers which may be tailored to individual particle sizes.

FIG. 1 shows an example of a filtration apparatus 100 comprising acyclonic particle separation chamber 102 and a liquid source 104.

The cyclonic particle separation chamber 102 has an inner surface 106.In use of the filtration apparatus 100, the liquid source 104 suppliesliquid to provide a flow of liquid on the inner surface 106.

Such a flow may trap particles incident thereon, for example when theparticles enter the flow, or by adhering to a surface of the liquidunder surface tension. Such trapped particles may be borne away by theflow. This prevents the particles from re-entering the air flow, as maybe the tendency of, in particular, lighter particles, and therefore awider range of particles may be efficiently filtered from the air thanif a cyclone of equivalent design with a ‘dry’ inner surface was used.

In some examples, the liquid may be water, which is innocuous andreadily available, although other liquids may be used.

The liquid source 104 may, in use of the apparatus, supply liquid so asto have at least one intended characteristic. For example, the liquidsource 104 may, in use of the apparatus, supply liquid so as to create asubstantially continuous flow (rather than a discontinuous flow in whichdry patches form), for example a flowing liquid film. The flow may beintended to have a given flow rate and/or thickness, and/or to extendaround a given portion of the inner surface.

The liquid source 104 may therefore supply liquid at a rate, and/or in adirection and/or with a dispersion so as to create a liquid flow havingany, or any combination of such intended characteristics. This maycomprise supplying liquid in a manner which may depend on the type(and/or surface tension) of the liquid used, the steepness and materialof the inner surface on which the flow is formed, the ambienttemperature and the like.

In practical terms, the filtration apparatus 100 may be for use with agiven liquid flowing on an inner surface 106 of a cyclonic particleseparation chamber 102 fabricated of particular materials and having anintended orientation, and there may be a predetermined range ofoperational temperatures. Once such factors are determined, a supplyrate to provide an intended liquid flow may be determined, for exampleanalytically using modelling or experimentally. At least one rate offlow may be predetermined and where a plurality of rates of flow arepredetermined, a rate may be selected based on any, or any combinationof, the local conditions, materials, an intended thickness of the flowon the inner surface 106 or the like.

In some examples herein, the liquid supply rate may be controlled by thesize of at least one liquid inlet to the cyclonic particle separationchamber 102. For example, the dimensions of such a liquid inlet may beselected to provide a flow rate and/or fluid dispersion though the inletwhich forms the liquid flow on the inner surface 106 so as to have atleast one intended characteristic (for example so as to be a continuousliquid flow, to coat the substantially the entire inner surface 106, tobe a laminar liquid flow or film, and/or to have an intended thickness,or the like). Liquid may be continuously supplied to such an inlet,which acts as a valve, controlling the amount of liquid entering thecyclonic particle separation chamber 102 such that a flow having theintended characteristic(s) is formed. In some examples, it may beintended to create a flowing liquid film of a predetermined thickness(or a thickness within a predetermined range), and/or a film whichexhibits at least substantially laminar or streamline flow (withoutcross currents, eddies and/or swirls, and/or without substantialturbulence), and a size and/or shape of an aperture or set of aperturesto form the inlet(s) may be selected accordingly. However, it may beunderstood that for a different operating condition (e.g. temperature,air flow rate, or the like), selected liquid, cyclonic particleseparation chamber 102, or the like, the dimensions of an inlet whichproduce such a liquid film may be different. In other examples, aturbulent flow condition may be provided or develop in view of thecyclonic air flow and/or an element of horizontal liquid flow may beintroduced by action of the cyclonic air flow.

In some examples, an inlet may be ‘oversized’ such that it could allowliquid therethrough at a higher flow rate than is indicated to form anintended flow on the inner surface, and the rate at which liquid issupplied thereto may be controlled to provide the conditions to form aflow having intended characteristics.

FIG. 2 shows another example of a filtration apparatus 200 andcomponents in common with FIG. 1 are labelled with like numbers. In thisexample, the cyclonic particle separation chamber 102 comprises achamber wall 202, and the inner surface 106 is disposed on the chamberwall 202. The chamber wall 202 comprises a liquid inlet slot 204 toallow liquid to enter the cyclonic particle separation chamber 102.

In this example, the liquid source 104 comprises a liquid reservoir 206to supply a liquid to the liquid inlet slot 204. The reservoir 206 is anannular reservoir and the liquid inlet slot 204 is disposed about thecircumference of the chamber wall 202.

In some examples, the inlet slot 204 may extend around substantially thewhole circumference such that a liquid film 208 provided over at leastsubstantially the whole of the inner surface 106. This may reduceturbulence in the air flow (for example, the rotational air flow) withinthe chamber. In some examples, such a liquid film may be provided by aplurality of inlets which are designed to disperse the liquid theydispense over an area, or by providing a close packed array ofindividual inlets, or in some other way. In still other examples, justparts of the inner surface 106 may have a liquid film 208 thereon.

The filtration apparatus 200 further comprises a liquid supply mechanism210, in this example comprising a liquid recirculation mechanism 212comprising a pump 214 and a filter 216. The liquid supply mechanism 210is controlled by a controller 218.

The liquid supply mechanism 210 is to supply liquid to the reservoir 206at, at least on average, the rate at which liquid enters the cyclonicparticle separation chamber 102. In other words, the reservoir 206 iskept partially full in use of the filtration apparatus 200. The inletslot 204 may have dimensions (e.g. a width) such that the liquid flowtherethrough is capable of providing a liquid film 208 of an intendedthickness. The intended thickness of the liquid layer may be selectedbased on the particle size and/or anticipated concentration within theair. The size of the aperture provided by the inlet slot 204 in thisexample controls the flow rate therethrough and the liquid supplymechanism 210 may, under the control of the controller 218, match thisrate of flow. This may be determined experimentally or analytically ormay be measured by a flow meter, for example at the point at whichliquid enters the cyclonic particle separation chamber 102 or as theliquid collects at the base thereof. In this example, the inlet slot 204is of a fixed size but in other examples, the size of the inlet may bevariable, for example under the control of the controller 218. In otherexamples, the controller 218 may control a rate of supply of liquid suchthat the liquid flow has intended characteristics and/or at least onedimension of an inlet.

The pump 214 and the filter 216 recirculate the liquid which has passedthrough the cyclonic particle separation chamber 102. It will beappreciated that, as it exits the cyclonic particle separation chamber102, the liquid may carry particles. While in other examples, a freshsupply of liquid may be provided and/or unfiltered liquid may berecirculated for at least a plurality of cycles, in this example, theliquid is filtered to remove at least a proportion of the particles andrecirculated. The filter 216 may for example comprise a sponge or meshfilter to capture the particles. In other examples, the liquid supplymechanism 210 may be a pipe or tube connected to a mains water supply,or any other static liquid supply point which may in some examplessupply a fluid under pressure.

FIG. 3 is an example of a method, which may be a method of filteringand/or separating particles from an air flow. Block 302 comprisescreating a flow of liquid on an interior surface of a cyclonic particleseparation chamber. This may comprise providing at least one apertureand arranging for liquid to flow therethrough at a flow rate which issuitable for forming a liquid flow on the surface, for example a flowingliquid film. In some examples, the size and/or shape of the aperturesmay be designed, configured or adjusted to supply liquid to the interiorof the surface to create a liquid flow having intendedcharacteristic(s). In some examples, the rate at which liquid issupplied to at least one aperture may be controlled so as to supplyliquid to the interior of the surface to create a liquid flow havingintended characteristic(s). In some examples, block 302 may comprisesupplying liquid to a reservoir which feeds liquid inlet to the cyclonicparticle separation chamber with a stable flow of liquid (for example,the flow rate through the inlet may be, at least on average,substantially equal to the rate at which liquid is supplied). In sameexamples, block 302 comprises creating the flow of liquid on theinterior surface of a cyclonic particle so as to have intendedcharacteristic(s) (e.g. one or more of an intended thickness, flowcondition (e.g. laminar or turbulent), flow rate, surface coverage orthe like).

Block 304 comprises supplying a gas to be filtered to the cyclonicparticle separation chamber. In some examples, the gas may be air. Insome examples, the gas may be gas from a chamber (e.g. a fabricationchamber) of an additive manufacturing apparatus.

Block 306 comprises generating a helical air flow within the chamber tourge particles in suspension in the gas to become trapped by the liquidflow. For example, this airflow may be created using a fan or the like.As both large and small particles may be, at least at some point in thehelical cycle, urged towards the edge of the chamber, this allows suchparticles to be captured by the liquid before they can become recapturedby the helical air flow and potentially escape the cyclonic particleseparation chamber.

FIG. 4 is another example of a method, which may be a method ofrecirculating liquid to form the liquid flow of block 302. The methodcomprises, in block 402, filtering the liquid to remove particles fromthe liquid. For example, the liquid may be collected at the base of thecyclonic particle separation chamber and passed through a filter. Block404 comprises recirculating the filtered liquid to form the liquid flow.For example this may be carried out through use of a pump or the like.

In some examples, the methods of FIG. 3 and/or FIG. 4 or parts thereofmay be carried out using the filtration apparatus 100, 200 describedabove.

FIG. 5 is an example of an additive manufacturing apparatus 500comprising a chamber 502 and a cyclonic cooling apparatus 504 to coolthe chamber 502 by extracting air therefrom. The cyclonic coolingapparatus 504 comprises a cyclonic particle separation chamber 506having an annular liquid inlet 508 and a liquid supply mechanism 510. Inuse of the additive manufacturing apparatus 500, liquid supplied to theannular liquid inlet 508 by the liquid supply mechanism 510 isintroduced into the cyclonic particle separation chamber 506 so as toform a flowing liquid film on an interior surface 512 thereof. Theadditive manufacturing apparatus 500 may be for use in any part of anadditive manufacturing process and the chamber 502 may for examplecomprise a fabrication chamber, a build material processing chamber or apost processing chamber of additive manufacturing apparatus.

The liquid film may trap particles in the air flow and this allows airwhich is drawn from a chamber 502 of an additive manufacturing apparatus500 to be efficiently filtered before being exhausted to the atmosphere,thus removing particles which may otherwise enter the atmosphere, forexample a room in which the additive manufacturing apparatus 500 isprovided.

The cyclonic cooling apparatus 504 may comprise any of the components ofthe filtration apparatus 100, 200 described above in relation to FIG. 1and FIG. 2. For example, the liquid supply mechanism 510 may comprise apump 214 to recirculate liquid which has passed through the cyclonicparticle separation chamber and/or a filter 216 to filter such liquid.In some examples, the liquid supply mechanism 510 may be a pipe or tubeconnected to a mains water supply, or any other static liquid supplypoint which may supply a fluid under pressure. The annular liquid inlet508 may allow fluid to enter the cyclonic particle separation chamber506 from an annular reservoir. The annular liquid inlet 508 may extendaround all, substantially all, or part of cyclonic particle separationchamber 506.

The additive manufacturing apparatus 500 may comprise additionalcomponents. Far example, further cyclonic coaling apparatus 504 may beprovided. In other examples, a print bed may be provided within theapparatus, which in some examples may be lowered as an object isgenerated such that the layer of an object which is being formed is at asubstantially constant height. Further components may comprise a printhead, a heat lamp, a build material spreader carriage, powder mixingapparatus or the like. The additive manufacturing apparatus may generateobjects in a layer-wise manner from a powder-like build material.

The present disclosure is described with reference to flow charts andblock diagrams of the method, devices and systems according to examplesof the present disclosure. Although the flow diagrams described aboveshow a specific order of execution, the order of execution may differfrom that which is depicted.

Some examples in the present disclosure may utilise machine readableinstructions, such as any combination of software, hardware, firmware orthe like. Such machine readable instructions may be included on acomputer readable storage medium (including but is not limited to discstorage, CD-ROM, optical storage, etc.) having computer readable programcodes therein or thereon.

The machine readable instructions may, for example, be executed by ageneral purpose computer, a special purpose computer, an embeddedprocessor or processors of other programmable data processing devices torealize the functions described in the description and diagrams. Inparticular, a processor or processing apparatus may execute the machinereadable instructions. Thus functional modules of the apparatus anddevices (for example, the controller 218) may be implemented by aprocessor executing machine readable instructions stored in a memory, ora processor operating in accordance with instructions embedded in logiccircuitry. The term ‘processor’ is to be interpreted broadly to includea CRU, processing unit, ASIC, logic unit, or programmable gate arrayetc. The methods and functional modules may all be performed by a singleprocessor or divided amongst several processors.

Such machine readable instructions may also be stored in a computerreadable storage that can guide the computer or other programmable dataprocessing devices to operate in a specific mode.

Such machine readable instructions may also be loaded onto a computer orother programmable data processing devices, so that the computer orother programmable data processing devices perform a series ofoperations to produce computer-implemented processing.

Further, some teachings herein may be implemented in the form of acomputer software product, the computer software product being stored ina storage medium and comprising a plurality of instructions for making acomputer device implement the methods recited in the examples of thepresent disclosure.

While the method, apparatus and related aspects have been described withreference to certain examples, various modifications, changes,omissions, and substitutions can be made without departing from thespirit of the present disclosure. It is intended, therefore, that themethod, apparatus and related aspects be limited only by the scope ofthe following claims and their equivalents. It should be noted that theabove-mentioned examples illustrate rather than limit what is describedherein, and that those skilled in the art will be able to design manyalternative implementations without departing from the scope of theappended claims. Features described in relation to one example may becombined with features of another example.

The word “comprising” does not exclude the presence of elements otherthan those listed in a claim, “a” or “an” does not exclude a plurality,and a single processor or other unit may fulfil the functions of severalunits recited in the claims.

The features of any dependent claim may be combined with the features ofany of the independent claims or other dependent claims.

1. A filtration apparatus comprising: a cyclonic particle separationchamber having an inner surface; and a liquid source to supply liquid toprovide a flow of liquid on the inner surface.
 2. A filtration apparatusaccording to claim 1 comprising at least one liquid inlet to thecyclonic particle separation chamber, wherein at least one dimension ofthe liquid inlet is selected to provide a flow rate though the liquidinlet which forms the flow of liquid on the inner surface so as to havean intended characteristic.
 3. A filtration apparatus according to claim1 wherein: the cyclonic particle separation chamber comprises a chamberwall, and the inner surface is disposed on the chamber wall, the chamberwall comprising a liquid inlet slot to allow liquid to enter thecyclonic particle separation chamber; and the liquid source comprises aliquid reservoir to supply a liquid to the liquid inlet slot.
 4. Afiltration apparatus according to claim 3 wherein the liquid inlet slotis disposed about a circumference of the chamber wall.
 5. A filtrationapparatus according to claim 3 further comprising a liquid supplymechanism, wherein the liquid supply mechanism is to supply liquid tothe liquid reservoir at a rate matched to a rate at which liquid entersthe cyclonic particle separation chamber.
 6. A filtration apparatusaccording to claim 1 further comprising a liquid recirculation mechanismcomprising a pump.
 7. A filtration apparatus according to claim 6 inwhich the liquid recirculation mechanism further comprises a filter. 8.A filtration apparatus according to claim 1 further comprising acontroller, the controller being to control a rate of supply of liquidso as to form the flow of liquid on the inner surface to have anintended characteristic.
 9. A method comprising: creating a flow ofliquid on an interior surface of a cyclonic particle separation chamber;supplying a gas to be filtered to the cyclonic particle separationchamber; and generating a helical air flow within the cyclonic particleseparation chamber to urge particles in suspension in the gas to becometrapped by the flow of liquid.
 10. A method as claimed in claim 9further comprising: supplying liquid to a reservoir which feeds a liquidinlet to the cyclonic particle separation chamber with a stable flow ofliquid.
 11. A method as claimed in claim 9 further comprising filteringthe liquid once it has flowed over the interior surface to removeparticles from the liquid.
 12. A method as claimed in claim 11 furthercomprising recirculating the filtered liquid to form the flow of liquid.13. An additive manufacturing apparatus comprising: a chamber and acyclonic cooling apparatus to cool the chamber by extracting airtherefrom, the cyclonic cooling apparatus comprising a cyclonic particleseparation chamber having an annular liquid inlet and a liquid supplymechanism, wherein, in use of the apparatus, liquid supplied to theannular liquid inlet by the liquid supply mechanism is introduced intothe cyclonic particle separation chamber so as to form a flowing liquidfilm on an interior surface thereof.
 14. An additive manufacturingapparatus according to claim 13 in which the liquid supply mechanismcomprises a pump to recirculate liquid which has passed through thecyclonic particle separation chamber.
 15. An additive manufacturingapparatus according to claim 14 in which the liquid supply mechanismcomprises a filter to filter liquid which has passed through thecyclonic particle separation chamber.